The most important source of opals in Australia was discovered at Coober Pedy in South Australia in 1914. This town is particularly unusual because most of it is built underground away from the hot desert air. The other most important sources of opals are in Andamooka (SA), Lightning Ridge (NSW) and White Cliffs (NSW). Australia continues to produce the vast majority of the world’s supply of these precious stones. In the late 1980s opal production in Australia was worth more than $100 million a year. The world’s largest opal stones have also been found in Australia.